Photothermal modulated reflectance (PMR) technique, being a physical basis for the ion-implant monitoring systems, is a well-known characterization methodology used for a variety of industrial and research applications. See for example, U.S. Pat. Nos. 4,579,463; 4,854,710 and 5,978,074, each of these references are hereby incorporated in their entirety herein by reference.
Photothermal IR radiometry (PTR) is a new emerging technology that has a number of potential advantages over existing methodologies in the characterization of electronic properties of semiconductors. In the PTR system and method, the optically induced emission of blackbody radiation (infrared radiation) at the surface of a semiconductor is measured by a remote IR sensitive detector. See e.g., “Laser Infrared Photothermal Radiometry of Semiconductors; Principles and Applications to Solid State Electronics” Mandelis, Solid State Electronics, Volume 42, No. 1, page 1, 1998; the entirety of this reference is hereby incorporated herein by reference; U.S. patent application Ser. No. 2002/0011852, publication date Jan. 31, 2002 (NON-CONTACT PHOTOTHERMAL RADIOMETRIC METROLOGIES AND INSTRUMENTATION FOR CHARACTERIZATION OF SEMICONDUCTOR WAFERS, DEVICES AND NON ELECTRONIC MATERIALS) (this reference is hereby incorporated herein by reference).
Investigations have been performed comparing these two techniques. For example, it has been shown that the PTR signal is extremely sensitive to the carrier plasma wave effects in semiconductors and possesses up to five orders of magnitude higher plasma-to-thermal contrast than that of the PMR method. See, “Relative Sensitivity of Photomodulated Reflectance and Photothermal Infrared Radiometry to Thermal and Carrier Plasma Waves in Semiconductors,” Salnik, et al., Journal of Applied Physics, Volume 82 (4) page 1853, Aug. 15, 1997; the entirety of this reference is incorporated herein by reference. Given the different characteristics of PTR measurement and PMR measurements, there can be instances where it would be desirable to make both PTR and PMR measurements on a wafer sample. In the past to make both PTR and PMR measurements on a semiconductor wafer, two different measurement devices were needed. Thus, it was necessary to move the wafer sample from one measurement device to another measurement device in order to make both PTR and PMR measurements on the wafer, which resulted in not measuring at the same sample location with high accuracy. Further, the fact that PMR measurement apparatus and the PTR measurement apparatus are separate results in additional space requirement and additional expense. What is needed is a measurement apparatus, which combines both a PTR measurement system and a PMR measurement system.